Dist. 13, Art. 2, Q. 2
by St. Bonaventure
Source text: Public Domain Mark 1.0. English translation/apparatus/encoding: CC BY-NC 4.0, Wroot Press.
https://bonaventure.wrootpress.com/browse/2/d/13/q/bon-sent-II-d13-a2-q2
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### Question II. *Whether light is a substantial form, or an accidental [form].*

Secondly it is asked whether light is a substantial or an accidental form. And that it is a substantial form is seen [as follows].

*Foundations.*

1. The generation of substance is prior to that of accident: but light is described as the first of all corporeal forms to have been created; therefore it does not seem to be an accident, but a substance — or else that operation was disordered.

2. Likewise, a substantial form is more noble than an accidental [form]; but light is the most noble of corporeal forms, as Augustine says in many places: therefore, since many other corporeal forms are substances, it seems that light is a substantial form.

3. Likewise, light among all corporeals is most assimilated to the eternal light, as Dionysius shows in *On the Divine Names*, and most of all in power and efficacy: therefore if this whole [property] befits a substantial form more than an accidental one, it seems that light is a substance.

4. Likewise, no accident is the cause of a substance; but the light of a celestial body is the principle of drawing forth the vegetative and sensitive soul, which are substantial forms: therefore it seems that it is a substance.

5. Likewise, no accident is active through itself, since none exists through itself: therefore just as it is not through itself, so neither does it act through itself; but a luminous body, insofar as it is luminous, is active through itself: therefore it seems that light is not an accident to it, but a substantial form.

6. Likewise, no accident makes a grade and nobility in things according to specific differences on account of its own greater and lesser participation: but the bodies of the world, according as they participate more or less of light, are more or less noble as regards *substantial being*, and differ in species, as is clear when one looks at the grades in the bodies of the world: therefore it is impossible that light be an accident of the luminous body.

*On the contrary:*

1. Nothing belongs to the constitution of an accident except an accident; but light belongs to the composition of color, since color is nothing other than *incorporated light*: therefore since color is an accident, light is an accidental form.

2. Likewise, nothing is *per se* the object of sense except an accident, because every object of sense is placed in the third species of quality; but light by itself is seen and perceived by the sense of sight, and is that by means of which other things are sensed, as Augustine says on *Genesis according to the Letter*, book 12: therefore light is an accident. For Augustine speaks thus: «*Sight operates by pure light, hearing by light incorporated in the most subtle air,*

*then light mixed in murky air, then with corpulent moisture, finally with earthly thickness — and so it produces the five senses*».

3. Likewise, that which is augmented in something, with its substance and nature preserved, is itself an accident to it; but light is augmented in bodies, especially luminous ones, as is said in Isaiah 30: *The light of the moon shall be as the light of the sun, and the light of the sun sevenfold*, etc.: therefore light is not a substance, but an accident, since substance does not receive more and less.

4. Likewise, just as fire naturally shines, so also it naturally is hot, nor is there a greater power in its shining than in its being hot or heating; but heat is an accidental quality of fire itself: therefore also luminosity.

5. Likewise, if light in fire is a substantial form, then either *ultimately completive* or *short of the ultimate*. If it is the *ultimate completive* form, then it seems that fire would not differ from the celestial nature, nor would any luminous [bodies] differ by specific difference. If it is a form *short of the ultimate*, then it is a less perfect form than the specific form of fire, since the ultimate completive form is in the most perfect thing: therefore it does not seem that in fire light is the most noble form. If, then, in heaven it is the ultimate form, it seems that elementary bodies are more worthy or noble than celestial — which if false, the rest follows, etc.

6. Likewise, in creatures quality is the *immediate* principle of action; hence a substantial form acts mediated by accidental properties as by instruments; but light is the *immediate* principle of action: therefore it seems that light is an accident.

### CONCLUSION.

> *Light, under one respect, is a substantial form; but under another, an accidental form.*

**I respond:** *Note.* It must be premised that in this question wise [men] hold contraries to wise [men].

*Opinion 1.* For some have wished to say that light is an *accident* of the luminous body, just as wisdom or knowledge, which is spiritual light, is an accident of the soul itself; and just as color is an accident of a determinate body; and just as heat is an accident of a hot body. For they said that the luminous body stands to light as the soul to cognition, as the determinate body to color, and as the hot body to heat — since through it [the body] is adorned, through it is sensed, and through it operates; and on this account, if [light] be called a noble form, this is not understood as regards *first being*, but as regards *second being*, just as knowledge and grace are posited as most noble forms, although they are said to be accidents. And thus for the most part the [contrary] reasons are evaded. — *It is not entirely proven.* But since sacred Scripture commends light among other purely corporeal forms, and the Catholic treatise-writers — such as Dionysius in the fourth [chapter] of *On the Divine Names*, and Augustine in many places, and the philosophers also — attribute the principate of operation in bodies to light: therefore they seem to hold that light is rather a substance than an accident.

*Opinion 2, conclusion.* And therefore there is another position: that light is a *substantial* form of bodies, according to whose greater or lesser participation bodies have more truly and worthily *being* in the genus of beings. Hence the most noble

of bodies, as is that empyrean, is principally luminous; the lowest, on the other hand, like earth, is most opaque; and the intermediate, according as they are more or less noble, participate more or less. And that all bodies participate the nature of light, this is shown plainly enough by the fact that there is scarcely any opaque body which by much rubbing and polishing cannot be made luminous, as is clear when out of ashes glass is made, and out of earth a carbuncle.

But each of these positions is *of great [authors]*, and each [is] very probable, nor can [either] be easily disproved. If, however, we wish to consider inwardly which of these positions is the truer, we shall find that each of them was founded upon some truth. For it is true that light, since it is the most noble form among corporeals — as the philosophers and the Saints say — according to whose greater and lesser participation bodies are more and less beings, is a *substantial form*. It is also true that, since light is *per se* sensible, and is also an instrument of operation, and is augmentable and diminishable while the substantial form is preserved, it itself has the *nature of an accidental form*.

And on this account it must be noted, for the understanding of the authorities and reasons, that just as *incorporated* light is the principle of color in a determinate body — which color is an accident and a passive quality and is perceived by sense — so also light in a luminous body is the principle of a certain *fulgor* (radiance) which, after the manner of color, is an accident, and by means of which the luminous body is apprehended by sense. — *Distinction.* And in accordance with this, light can be taken in two ways. — *Conclusion 1.* In one way, light is called the very *form* which gives *being* to a shining body, and from which the luminous body is principally active, as from a first mover and regulator. — *Conclusion 2.* In another way, light is called the *fulgor* (radiance) itself, which is around the luminous body, which follows upon the existence of light in such matter, and which also is the object of sense and the instrument of operation; and so it is an *accidental complement*.

And thus the response to the proposed question is clear; the response to the objections is also clear for the most part. For the reasons showing that light is a substantial form proceed according to the *first* way, as is clear to one who looks. But the reasons on the opposite side proceed by the other way, except for some, to which it can easily enough be replied.

*Solution of the opposing [arguments].*

1. To that which is first objected — that light belongs to the composition of color — it can be said that light is not said to belong to the composition of color as an *intrinsic* principle, but as an *effective* principle, since accidents are simple; whereas a substantial form can well be the effective principle of an accident.

2. To that which is objected, that it is a sensible form: it must be said that it is not sensed by reason of its essence, but by reason of the *fulgor* or *color* inseparably accompanying it, especially where there is intensity of light.

3. *Note.* To that which is objected, that it is augmented: it must be said that that augmentation is regarded by reason of the *fulgor*, not by reason of the *light*, which is a substantial form; and even if it were regarded by reason of [the substantial form], the argument still would not hold, because although a substantial form *in itself* does not receive more and less, it nevertheless can be intensified and remitted according to its *being in matter*. And this is most true of *general* forms, in which there consists more the commonness of *analogy* according to more and less, and prior and posterior, than that of *univocation*.

4. To that which is objected, that heat is not the substantial form of the hot [thing]: it must be said that it is not similar, because the form of heat is not of as great dignity and perfection as the form of light. And this is clear, because the form of light recedes more from the nature of contrariety, corruption, and alteration.

5. To that which is objected, that it is not the ultimate form in fire: it must be said that if light is posited as the substantial form of bodies specifically diverse — as of the heaven and of fire — it is the ultimately completive form of neither. Therefore from this it is not concluded that the elementary nature is more noble than the celestial; nor can it from this be concluded that another form is more noble than the form of light, although it be further. — *On the twofold form, the common and the ultimate.* For the form of light, when it is posited in the same body with another form, is not posited as an *imperfect disposition* born to be perfected by the ultimate form, but is posited as the *form and nature conservative of every other corporeal form* and giving it efficacy of acting, and according to which is regarded the measure of any corporeal form in dignity and excellence. — And that which is objected, that the *ultimately completive* form is more noble — this is true where that form has to be completed and perfected by the ultimate, namely where the *common* form has to be perfected by the ultimate and special. — *Another solution.* Or it must be said that this holds true where

each form, namely *common* and *ultimate*, is in its [most] potent *being*; but light is not so [posited] except in a celestial body.

6. To that which is objected, that it is the immediate principle of operation: it must be said that this does not necessarily compel [the conclusion], as it appears; *Note.* for a substantial form seems to be able to act *per se*. But because an example of this is not easily found in others — although it would not be irrationally believed possible in the form of light, since it is most of all active — it can be conceded that, although light *inwardly perfecting* is a substantial form, nevertheless that *fulgor* by which that body operates instrumentally, [and which] is sensed and adorns [it], can not unlearnedly be believed to pertain to the nature of accident, as has been said.